One function that I regularly use on my HP 12C (next to simple arithmetic and statistics) is "Delta Days". While I really like the DM15L, missing this function (plus the option to substract or add a number of days to a given date) keeps me from using it as my work calculator.

I know there is a DM12L but a nicer option would be to have an implementation of the "Delta Days" function for the HP 15C. I am aware of some programs that compute a Gregorian date to a Julian date. However, I don't know about a program which does what the HP 12C can; pushing two dates on the stack, and returning the number of days between them.

Anyone aware of such a program, or one that could easily be adapted to the HP 15C / DM15L?

Quick update; there are many good things to the HP 12C for me, even when I hardly use any of the financial functions:

Several data calculations (date plus days, difference between days, day of the week)

Percentage functions are available as primary functions on the keys

Statistical functions are in the same place as on the 15C

12x and 12/ functions are sadly missing from the 15C (difference is only one keystroke, but those keys are in my muscle memory )

So while I'd love to use the DM15L as my primary calculator, I have to admit that the 12C layout works better for me. Which means that the 12C is back on my desk, while the DM15L is at home as a fun calculator.

So the next questions is of course ... should I splurge on a DM12L or keep using my Singapore made HP 12C until it dies?

So the next questions is of course ... should I splurge on a DM12L or keep using my Singapore made HP 12C until it dies?

The DM12L is much faster than older (3-battery or 1-battery) 12Cs, so if you use programs this may be a strong factor to consider. I'm not sure of the relative performance of the DM12C as compared to the newest 2-battery machines (often called the 12C+), these are literally over 100 times faster than the older 12Cs. Also, the DM12C has the clock built-in, which may be useful too.